1. Field of the Invention
This invention relates to stops used in controlling the feeding of material as a workpiece to a machining operation, such as cutting a length of the material on a band saw, and more particularly, to an adjustable stop which compensates for undesired movement of the workpiece. The stop is illustrated in conjunction with a shuttle vise on a band saw, but the stop may be used in other applications, such as the feeding of material to a punch press, etc.
2. Description of the Prior Art
Machines for cutting material, such as large band saws which are used to cut workpieces formed of elongated materials, are well known in the art. The workpiece material is positioned on a feed conveyor adjacent to the saw blade and moved into a cutting position under the saw blade by a shuttle vise which is moved to a clamping position to initially clamp the material and then move in a direction toward the saw blade and to a cutting position. A stop is sometimes used to limit movement of the shuttle vise and to insure it stops at the desired cutting position. As the material is moved, it extends beyond the saw blade onto a receiving conveyor where it is clamped by a fixed vise adjacent to the saw blade. At this point, the material is cut by the saw blade. While the saw blade is cutting, the shuttle vise is released from the material and moved back to the desired clamping position to clamp the material again and move it to the cutting position for the next cutting operation. This type of saw works well for many applications where the cut length of the material is not particularly critical.
However, in cases where the cut length of the material may be critical this prior art saw may not be able to position the material in the cutting position accurately enough to insure that the cut length is within the desired tolerances. Closer tolerance requirements are becoming more common. The problem has to do with the straightness of the material, surface imperfections, and/or flexibility of the material and the deflection thereof when clamped by the shuttle vise. When the vise clamps the material, the clamping action may actually cause the shuttle vise to move slightly due to these variations in the material. This means that the shuttle vise is moved away from or toward the stop with the result that the cut length of the material may be correspondingly longer or shorter than desired. Obviously, if the movement of the shuttle vise can be greater than the cut length tolerances on the workpiece, this is very undesirable.
The present invention solves this problem by providing an adjustable stop to compensate for the amount of undesired movement of the shuttle vise and transmitting a signal to a controller which adjusts the position of the stop. Thus, when the shuttle vise moves to the cutting position and engages the adjusted stop, the cut length of the material will be at the proper length. That is, the adjustment of the stop compensates for the undesired movement of the shuttle vise so that the cut length of the material stays within the desired tolerances. Also, the encoder will detect the incorrect position of the shuttle vise and will adjust the front stop to compensate for the positional error in the shuttle vise. In addition to this positional adjustment, when the shuttle vise clamps the material to be cut, the encoder will detect variances which occur while clamping and will make an adjustment for that error also.
It will be understood by those skilled in the art, that this adjustable stop apparatus is useful in any application in which material is clamped and moved. Accordingly, the invention is not intended to be limited to a band saw application.